90 ezgo engine swap questions!

[fonz3482]

hello everyone,
I havent had much time to mess with my 1990 ezgo lifted cart, but last summer the thing gave me nothing but problems. It ran poorly, kept fouling plugs, and even stopped starting altogether. A friend that has a golf cart repair shop has offered me some help in checking the motor out, but my concern is it will need some major repairs. Also, before when it was running the stock 2 stroke engine was lacking in power, and speed for what I would like to do with it. The cart is lifted 8" and I would like to use it to bomb around my 2 acres of hilly land, my grandpa's 30 acres, and my dads 27 acres. So Im mostly looking for some more power, and alittle more speed(@ 30mph). I was thinking of swapping in a snowmobile motor. But Im concerned about a few things. Will a sled engine run good in warm weather?, do they swap in easily. Will I be able to still use reverse?? what cc engine should I start with. I have a gentleman offering me a running kawasaki 440, would this be a good motor?? Please all the experts chime in!! I can use the help!!